A transparent displaying system typically consists of an image source and an imaging window. In existing transparent displaying systems, there are a variety of choices for the image source and the imaging window. An imaging window is usually composed of a substrate and a reflective surface, and most of the imaging windows adopt the structure in which the reflective surface serves as an interlayer in the substrate.
In the prior art, there are technical solutions utilizing a source emitting p-polarized light as the image source. For example, an imaging method using p-polarized light is mentioned in Chinese Patent Publications CN204143067U and CN104267498A, U.S. Pat. Nos. 6,952,312B2; 7,123,418B2; and 7,355,796B2, and European Patent Application EP0836108A2.
These p-polarized light based imaging methods, however, generally have the following drawbacks: if a relatively high reflectivity is required, then the transmissivity will be lowered, thereby reducing the viewing effect of the external environment, resulting in a relatively high demand on the brightness of the image source.
For example, when such methods are applied to a head-up display, a dark spot will be formed in the front window. If a relatively high transmissivity is required, the reflectivity will be lowered; in order to achieve a good imaging effect, there will be a relatively high demand on the brightness of the image source, which increases cost on power dissipation of the image source and the like.
In the prior art, a technique using a source that emits s-polarized light as the image source has been proposed. For example, U.S. Published Patent Application No. US2005012682 and Japanese Patent JP2-141720A both mention an imaging method using s-polarized light. However, such s-polarized light-based imaging methods have the following drawbacks:
1. a ghost image can be easily generated;
2. if a relatively high reflectivity is required, then the transmissivity will be reduced, thus reducing the viewing effect of the external environment.
Chinese patent CN2694293Y discloses a full color multiband stack film applied in a head-up display which utilizes the interference principle of the multi-layer film of the dielectric layer. The disadvantage of this technique is that the transmissivity of light of a specific wavelength is not high. For example, the low transmissivity for particular wavelengths such as red, green, blue light will greatly reduce the light (red, green, yellow light) emitted from traffic signal lamps, causing a potential safety hazard. Moreover, the imaging angle of the technique is limited, and the imaging effect is not good; besides, the technique requires coating about 70 layers of films, so that the manufacturing process is too complicated.